1. Field of the Invention
The invention relates to a non-return valve comprising a valve member having a circumferential face and a channel with a mouth on either side, the mouth at one end of the channel being sealable by a valve element capable of releasing said one mouth at a predetermined pressure in the channel higher than an ambient pressure, which valve element comprises an O-ring manufactured from an elastic material, such as a rubber or a resilient plastic, and which one mouth of the channel is located in a groove sealed by the valve element and having circumferential edges provided on parts which are adjustable and fixable relative to each other.
2. Background Art
Such non-return valve is known from German patent specification 201161, wherein the desired blow-off pressure in the channel can be set through a suitable choice of dimensions, design and material of the O-ring and the dimensions and design of the groove in which the sealing O-ring is located. In this known construction, the width of each groove is determined by three adapters that are locally accommodated in the groove with clamp action. For retensioning the O-ring, the non-return valve must be disassembled, the adapters must be replaced by slightly shorter adapters and the non-return valve must subsequently be reassembled. Because of the amount of parts, this operating procedure is not only expensive, labor-intensive and susceptible to failure, but also requires keeping in stock various adapters with a range of accurately determined lengths.